Yakuno Ophiolite

Invalid synonym: Yakuno Rocks, Yakuno Complex

Ultramafic -mafic rocks with associated basalts and metamorphic rocks in Maizuru Belt. Similar rocks in North zone and Central zone are called as this field name.

Type locality: Yakuno town, Fukuchiyama city, Kyoto prefecture
Middle - lower crust of a Paleozoic volcanic island arc (Yakuno paleo-island arc) in the ocean
Ophiolite originated from oceanic type, island-arc type and back-arc basin type oceanic crusts
Mafic rocks: Silurian - Carboniferous (426 - 341 Ma, Nd-Sm)
Meta-gabbro: Carboniferous - Permian (343 Ma, Nd-Sm, 270 - 250 Ma, K-Ar)
Granitoids: early Permian (285, 282 Ma, U-Pb)

Sedimentary facies: Marine
Sedimentary facies (Oshima, Fukui pref.): Ocean floor crust
Sedimentary facies (Ayabe, Kyoto pref.): Ocean floor crust
Sedimentary facies (Yakuno, Kyoto pref.): Back-arc basin
Sedimentary facies (Kamigori, Hyogo pref.): Island-arc crust
Sedimentary facies (Ohara, Okayama pref.): Island-arc crust
Lithofacies: Meta-gabbro
Lithofacies (Minor): Diabase, Ultramafic rocks, Granitoids, Mica gneiss
Lithofacies (Yakuno, Kyoto pref.): Meta-basalt, Meta-dolerite, Meta-gabbro
Lithofacies (Yakuno, Kyoto pref., Minor): Troctolite
Lithofacies (Kamigori, Hyogo pref.): Cumulate from tholeiitic magma of an island arc
Lithofacies (Kamigori, Hyogo pref., Minor): Mafic rocks originated from shoshonite
Lithofacies (Ohara, Okayama pref.): Cumulate from tholeiitic magma of an island arc
Lithofacies (Ohara, Okayama pref., Minor): Mafic rocks originated from shoshonite

Lower limit: Thrust fault (Ultra-Tamba Belt, Hiraki Formation, Tatsuno Formation)

Asago area, Hyogo pref.
[ North ]
/--/--/--/--/-
Upper sheet
/--/--/--/--/-
Middle sheet
/--/--/--/--/-
Lower sheet
/--/--/--/--/-
[ South ]

Okayama pref.
[ Upper ]
?--?--?--?--?-
Tonoshiki Formation
?--?--?--?--?-
[ Lower ]

South zone
[ North ]
/--/--/--/--/-
Yakuno Ophiolite
/--/--/--/--/-
[ South ]

Maizuru Belt
[ North ]
/--/--/--/--/-
North zone
/--/--/--/--/-
Central zone
/--/--/--/--/-
South zone
/--/--/--/--/-
[ South ]

------ Conformity, ~~~~~~ Unconformity, ~~~--- Local unconformity, '''/,, Interfingered, :::::: Fault, /--/-- Thrust, +__+__ Ground surface, ?--?-- Unknown

Distribution: Fukui pref. - Kyoto pref. - Hyogo pref. - Okayama pref.
Distribution: Oshima peninsula, Fukui pref.; Ayabe city, Kyoto pref.; Yakuno town, Fukuchiyama city, Kyoto pref.; Asago city, Hyogo pref.; Kamigori city, Ako county, Hyogo pref.; Ohara - Kuroyabu, Mimasaka city, Okayama pref.

Kimura et al. (2019) Jour. Geol. Soc. Japan, vol.125, no.2, pp.153-165 DOI
Suda and Hayasaka (2009) Jour. Geol. Soc. Japan, vol.115, no.6, pp.266-287 DOI
Takemura et al. (2009) Jour. Geol. Soc. Japan, vol.115, Supplement, pp.123-137 DOI